Field of the Invention
The invention relates in general to an electronic device and a control method thereof, and more particularly to a multimedia device and a motion compensation method thereof.
Description of the Related Art
In response to the requirement of liquid crystal TV, more and more researches are focused in the field of motion estimation/motion compensation (ME/MC). Motion compensation is an algorithmic technique employed in the encoding of video data for video compression.
In general, motion estimation refers to a method for determining motion vectors from adjacent frames. The motion vectors describe the transformation from one frame to another. The motion vector can relate to the whole frame (global motion estimation) or specific parts thereof, such as rectangular blocks, arbitrary shaped patches or even per pixel. Furthermore, applying the motion vectors to a frame to synthesize the transformation to another frame is called motion compensation. The combination of motion estimation and motion compensation is a commonly used technology in image compression.
According to motion estimation/motion compensation, two frames to be displayed on the screen are analyzed, and a middle state of the two frames is estimated through calculation. That is, an interpolation frame is generated between the two frames. Referring to FIG. 1, a schematic diagram of an example of generating a middle frame by way of motion estimation/motion compensation is shown. Firstly, moving objects such as an object Obj on the two frames I-frame and P-frame are located by using motion estimation algorithm. Next, a motion vector MV, which denotes the movement path of the object Obj on the frame, is calculated according to the difference between the two frames I-frame and P-frame. Then, motion compensation algorithm is used for estimating the middle state of the moving object Obj according to the motion vector MV and the two frames I-frame and P-frame, thus generating an interpolation frame M-frame.
However, as regards blocks which are adjacent to a valid range of a frame, there often are problems in the estimation of the motion vector. For example, when a moving object is located around edges of a frame, such as a moving object moving into the range of the frame or leaving the range of the frame, the position of the object cannot be found in continuous frames. Consequently, applicable motion vectors cannot be generated, the accuracy in estimation is reduced, and the quality in frame interpolation deteriorates.